Conventionally, in the field of electrophysiology, a patch clamp method has been known as a method for measuring an ion channel function possessed by a cell membrane, and various functions of the ion channel have been clarified by this patch clamp method. In the cytology, there have been great concerns about the functions of the ion channel, and these are also applied to developments for medicines.
In the patch clamp method, however, since an extremely high measuring technique is required for inserting a fine micropipette into a single cell with high precision, a skilled technician is required. Therefore, when measurements with a high throughput are required, this method fails to provide an appropriate method.
For this reason, a flat-plate type probe, formed by utilizing a micromachining technique, has been developed, and this probe is suitably applied to an automated system that does not require the insertion of the micropipette to each cell individually. For example, a technique has been proposed in which: a hole is formed in a carrier that separates two areas, and by allowing electrodes placed above and below this carrier to generate an electric field, the hole is efficiently made in contact with a cell and allowed to keep this state efficiently, and electrical measurements are carried out between the upper and lower electrodes so that electrophysiological measurements can be carried out on the cell (see Patent Document 1). Moreover, another technique has been proposed in which; a plurality of through holes are formed in a flat-plate device, and a continuous layer of a cell adhered to these is used for measuring potential-dependent ion channel activities by using electrodes (see Patent Document 2).
Moreover, still another technique has been proposed in which: microelements respectively attached to the inside of each of a plurality of cavities formed on a substrate are prepared, and by pressure-reducing passages connected to these microelements, a cell is attracted to the microelements so that electrophysiological phenomena of the cell are measured (see Patent Document 3). Still another technique has been proposed in which: holes are formed in a flat portion of a substrate, and a reference electrode and a measuring electrode are integrally formed in the substrate so that electrophysiological phenomena of a cell are measured (see Patent Document 4). Furthermore, still another method has been proposed in which: on a surface through which one channel penetrates, a cell is positioned by a suction process applied from the lower surface of the cell, and one portion of the lower surface of the cell is ruptured by increasing a pressure difference so that the cell contained in a liquid is measured (see Patent Document 5).
Another apparatus has been proposed in which: an orifice is sealed by an object in use, and first and second cavity portions, electrically insulated by this object, are formed so that electrical measurements are carried out on the object in a medium based upon changes in impedance between the electrodes respectively placed on the first and second cavity portions (see Patent Document 6).
Still another technique has been proposed in which an extracellular potential measuring device, which has a well that has a cell holding means and is formed on a substrate, a measuring electrode used for detecting an electric signal of the well and a reference electrode, is used for measuring the extracellular electrical potential (see Patent Document 7).
Moreover, still another apparatus has been proposed in which: an orifice is sealed by an object, and by measuring an electrode impedance between cavities electrically insulated by the object, a change in the state of the object can be detected, and a liquid supplying means, provided with a liquid supplying capillary tube and a liquid suction capillary tube used for quickly removing or exchanging the liquid environment in which the object is placed, has also been proposed (see Patent Document 6).
In addition to these, a device in which through holes having a diameter of several μms are formed on a flat plate made from SiO2 has been known. These through holes have the same function as that of a tip hole that is formed in the glass pipette used in the patch clamp method. By conducting a suction process or the like on a cell from the back surface side of the flat plate, the cell can be automatically attracted to the through hole to adhere thereto; thus, it becomes possible to easily measure the extracellular electric potential.
However, the main objective of the above-mentioned conventional cell electrophysiological sensor is to easily measure electrophysiological phenomena of a cell, without the necessity of using a microprobe to be used in the conventional patch clamp method. In particular, the liquid supplying means, disclosed in Patent Document 6, is an effective means used for quickly removing or exchanging the liquid environment on the periphery of a cell. However, although it is very important to place an extremely thin pipe serving as the liquid supplying means on the periphery of a cell with high precision, to insert the pipe in the liquid with high precision is very difficult since in the liquid, the influence of a surface tension exerted onto the pipe is not negligible. Moreover, when, upon supplying a liquid on the periphery of a cell, a direct flow is generated toward the cell, the flow tends to be unstable in the case when the flow is made too strong so as to quickly supply the liquid.
Patent Document 1: Japanese Translation of PCT Publication No. 2002-508516
Patent Document 2: Japanese Translation of PCT Publication No. 2002-518678
Patent Document 3: U.S. Pat. No. 6,315,940
Patent Document 4: Japanese Translation of PCT Publication No. 2003-511668
Patent Document 5: Japanese Translation of PCT Publication No. 2003-511699
Patent Document 6: Japanese Translation of PCT Publication No. 2003-527581
Patent Document 7: International Publication WO02055653